I. Field of the Invention
The present invention relates to the support structure, or gantry, for an x-ray computed tomography (CT) scanner or the like.
II. Description of the Prior Art
X-ray CT scanners are known which comprise an x-ray assembly mounted on a rotatable support. Such rotatable supports typically comprise a fixed stator and a rotor rotatably mounted thereon by means of a ring bearing. The stator and rotor are hollow bore to permit the whole body of a patient to lie along the axis of rotation of the rotor. An x-ray source and x-ray optics, including a shutter, wedges, and a collimator, are all individually mounted to the rotor and aligned with respect to one another.
The x-ray source requires access to high voltage. High voltage cables may be employed to connect a stationary high voltage source to the rotatable x-ray source. However, the cables then inhibit the degree by which the x-ray source may be rotated about the patient, and preclude continuous rotation of the x-ray source.
To provide continuous rotation of the x-ray source, known gantry assemblies employ the use of a standard high voltage slip ring assembly. Such a slip ring assembly is known to have its own rotor and stator structures which are supported on its own ring bearing. Known slip ring configurations require liquid or gas high voltage insulation and attendant seals. These seals are subject to repeated failure, requiring easy access to the seals and/or the ability to easily replace the entire slip ring assembly. Still further, known slip rings require electrical connection in a manner which results in close proximity crossing of high voltage wiring of one polarity with ring electrodes of the opposite polarity. Such crossings have the tendency to result in high voltage breakdown.
Such known slip ring assemblies are constructed with a small diameter in order to minimize cost and in order to avoid disadvantages typically incumbent in large diameter slip rings. The diameter, accordingly, is typically too small to encircle a patient. The slip ring assembly is, therefore, located at one end of the gantry assembly, and an arm is used to connect the slip ring assembly to the rotor of the x-ray assembly. The resultant gantry assembly forms a closed-bore into which the patient must be inserted, precluding access to the patient and intensifying patient concern. Moreover, such prior art gantry assemblies have minimal, if any, ability to tilt the plane in which the x-ray source rotates.
A gantry assembly might attempt to employ a large diameter slip ring to avoid the disadvantage of a close-bore configuration. In such a device, the x-ray assembly and slip ring assembly could be positioned side-by-side with fins or the like physically interconnecting the two assemblies. Once again, however, the ability to tilt the plane of the x-ray source is limited. To maximize the degree of possible tilt, the internal diameter of both the x-ray and slip ring assemblies must be increased, but with incumbent increase in bulk cost and complexity of the resultant gantry assembly. More importantly, for given rotor rotational speeds, surface speeds increase with larger diameter assemblies, which increases the probability of seal failure and the failure of other components. In known gantry assemblies, cost is further increased by utilizing separate ring bearing assemblies, stator structures and rotor structure, for both the x-ray assembly and the slip ring assembly.
It is, accordingly, an object of the present invention to provide a gantry assembly which allows for continuous rotation of an x-ray source in an economical and efficient manner.
A further object of the present invention is to provide a continuous rotation gantry assembly which has an open bore configuration with a minimal gantry cross-sectional area and overall volume, thus permitting unrestricted patient access.
A still further object of the present invention is to provide a continuous rotation gantry assembly which readily permits tilting of the plane in which an x-ray source rotates.
A still further object of the present invention is to provide a continuous rotation gantry assembly in which the x-ray source and x-ray optics may readily be aligned at a location remote from the gantry assembly.
A still further object of the present invention is to provide a continuous rotation gantry assembly which minimizes the likelihood of high voltage breakdown.
Another object of the present invention is to provide a continuous rotation gantry assembly containing liquid or gas insulation seals which are not subject to repeated failure and which are easily accessible for replacement in the unlikely event of failure.
Additional objects and advantages of the present invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.